What kind of indices does PLS Graph generate
to tell you about the quality of the model's fit. I realize that the indices
used in EQS and LISREL (e.g., CFI, NNFI) will not be given, but Falk &
Miller (1992) talk about the RMS COV (E, U) (i.e., root mean square of the
covariance between the manifest variable residuals and the latent variable
residuals). I'm unable to find this in any of the outputs.

There are at least two difficulties/issues that come to mind when
considering model fit in PLS analyses. The first is whether all your
constructs are modeled as reflective. If not, fit indices dealing with
explaining covariation among your measures cannot be used. The other issue deals
with whether your emphasis is primarily focused on minimizing residual error and
maximizing explained covariation among all measures - or in maximizing variance
explained for certain constructs or measures.

If either of the two issues are being consider, the RMS index you
mentioned becomes problematic. So these and other such indices are currently not
included to avoid confusion. Someday we may add it contingent on the exact model
being examined.

"A
final issue is the over-reliance towards overall model fit (or goodness of
fit) indices. "Where is the goodness of fit measures?" has become
the 90s mantra for any SEM based study.Yet,
it should be clear that the existing goodness of fit measures are related to
the ability of the model to account for the sample covariances and therefore
assume that all measures are reflective.SEM procedures that have different objective functions and/or allow for
formative measures (e.g., PLS) would, by definition, not be able to provide
such fit measures.In turn,
reviewers and researchers often reject articles using such alternate
procedures due to the simple fact that these model fit indices are not
available.

In
actuality, models with good fit indices may still be considered poor based on
other measures such as the R-square and factor loadings.The fit measures only relate to how well the parameter estimates are
able to match the sample covariances.They
do not relate to how well the latent variables or item measures are predicted.
The SEM algorithm takes the specified model as true and attempts to find the
best fitting parameter estimates.If,
for example, error terms for measures need to be increased in order to match
the data variances and covariances, this will occur. Thus, models with low R-square
and/or low factor loadings can still yield excellent goodness of fit.

Therefore,
pure reliance of model fit follows a Fisherian scheme similar to ANOVA which
has been criticized as ignoring effect sizes (e.g., Cohen, 1990, p. 1309).Instead, closer attention should be paid to the predictiveness of the
model.Are the structural paths
and loadings of substantial strength as opposed to just statistically
significant?Standardized paths
should be around 0.20 and ideally above 0.30 in order to be considered
meaningful.Meehl (1990) has
argued that anything lower may be due to what he has termed the crud factor
where “everything correlate to some extent with everything else” (p. 204)
due to “some complex unknown network of genetic and environmental factors”
(p. 209).Furthermore, paths of
.10, for example, represents at best a 1 percent explanation of variance.Thus, even if they are “real”, are constructs with such paths
theoretically interesting?"